Wet wipes cut from fibrous web structures formed in a co-forming process have been marketed for several years. The co-forming process involves melt spinning continuous filaments from polymer resin, and simultaneously, directing an air stream with entrained distributed cellulose fibers together with the filaments, typically into a co-forming box or similar blending apparatus, blending the filaments and fibers, and directing the blend along to a collecting/forming structure such as a moving forming belt. The filaments may be spun and introduced into the airstream carrying the cellulose fibers, or an airstream carrying the cellulose fibers may be introduced into the pathway of the filaments following spinning, the effect being the deposit of an entangled blend of filaments and fibers onto the moving forming structure and accumulation and formation of a batt thereof. Upon subsequent consolidation and bonding of the batt, a cohesive fibrous web structure may be formed. The co-forming process is, advantageously, typically dry, in contrast to wet forming techniques often used to make products such as paper towels from cellulose pulp. The co-formed fibrous web structure may be used, for example, as a wet wipe substrate. The entangled polymer filaments in the co-formed structure provide a matrix that holds the relatively short fibers, entangled therewithin, in place within the structure, and thereby help maintain structural integrity of the structure when it is wetted with an aqueous lotion.
The fibrous web structure from which wet wipes (for example, baby wipes) are made, should be strong enough when moistened with a lotion to maintain structural integrity in use, but also soft enough to give a pleasing and comfortable tactile sensation to the user. In addition, the structure should have suitable absorbency, porosity and surface texture to be effective in absorbing, retaining and carrying an aqueous lotion, releasing the lotion under pressure during use, and in cleaning soiled skin, while at the same time providing a reliable barrier between the user's hand and the soil (e.g., fecal matter).
In addition, cost and environmental sustainability concerns impose pressure to further improve the performance of wipes to enable better cleaning with less material, without compromising lotion carrying and release and other important properties such as tensile strength and protection.
Recently, improvements have been introduced to the co-forming process and resulting fibrous web structure. As described in U.S. application Ser. No. 13/076,492, a co-formed fibrous web structure with improved absorption properties is described.
In addition to the other improvements described in that application, it is briefly surmised that layers formed of meltblown polymer filaments alone can be formed on the outermost surfaces of the co-formed batt prior to bonding, to beneficial effect. It is surmised that the addition of the meltblown layer (called “scrim”) can help reduce release of lint (comprising fibers dislodged from the structure) during use by a consumer.
However, the ways in which inclusion of scrim layers, and the relative proportions of components of the scrim layers and intermediate or core layers, affect properties such as tensile strength, drape, surface friction, opacity, texture and feel of the web material, have not been apparent or predictable. Thus, it would be beneficial if the best proportions of components overall, together with their allocations among the various layers or substructures, of a fibrous web structure having scrim layers, and any other improvements making the structure desirable for use as wet wipe substrate, could be identified.